<script>
  var color = 'blue';
  var str = 'The sky is '+color;
  var tel = 110 + '120';
  console.log(str);                          // 输出结果为：The sky is blue
  console.log(tel);                          // 输出结果为：110120
  console.log(typeof str, typeof tel);       // 输出结果：string string
</script>